FIG.9 shows an example of the conventional ion flow type electrostatic recording head which is described in, for example, Japanese Patents JP-A-59-164,154, JP-A-59-190854 and JP-A-2-38070. Referring to FIG. 9, an ion generator is formed of one elongated discharge wire 51 and a metal shield 52 surrounding the discharge wire 51. The metal shield provides an opposite electrode to the discharge wire. This shield 52 has an ion exhaust path 53 and a compressed air introducting path 54. In the ion exhaust path 53, a control electrode head is provided. The control electrode head has a large number of elongated parallel electrodes 55 extending toward the ion exhaust path 53. When a DC high voltage of 5 to 7 kV is applied to the discharge wire 51, corona discharge occurs between the discharge wire 51 and the shield 52, causing discharge of a large amount of ions from the circumference of the discharge wire. The produced ions are introduced into the ion exhaust path together with the compressed air. On the other hand, an image control voltage of 50 to 100 V is selectively applied to the control electrodes 55 so that from among the ions introduced into the ion exhaust path, those ions existing near the electrodes 55 to which the control voltage is applied are passed through the ion exhaust path and projected toward a recording medium 56 by the electric field produced by the electrodes, while those ions existing near the electrodes 55 to which the control voltage is not applied are prevented from passing through the ion exhaust path. Thus, an electrostatic latent image is formed on the recording medium 56 in accordance with the distribution of those control electrodes 55 to which the control voltage is applied.
However, the conventional recording head involves a problem such that because of the presence of a strong electric field in the ion generating section, dust (chiefly. SiO.sub.2) in air, for example, is deposited on the discharge wire which is provided in the ion generating section, resulting in irregular discharge and leak of discharge. In other words, the ion generation by using the discharge wire involves a problem of poor durability.
In addition, in the ion generation using the discharge wire, corona discharge radially occurs toward the shield around the ion generating section, so that ions are diffused. Thus, the ions generated by discharge are not efficiently drawn out from the ion exhaust path. Particularly in case of high speed image production where much ion flow is required, this problem is more serious.